Exercise bike



FIG. 1 is a top, front, left perspective view of an exercise bike showing our new design;

FIG. 2 is a top, front, right perspective view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a top view thereof;

FIG. 8 is a top, rear, left perspective view thereof; and,

FIG. 9 is a top, rear, right perspective view thereof.

The broken lines depicting the remainder of the exercise bike show features that form no part of the claimed design. 

CLAIM The ornamental design for an exercise bike, as shown and described. 